In Ghana, rough lemon (Citrus lirnnn L.). grown extensively in citrus nurseries for rootstock material, has shown a high incidence of leaf spot with occasional leaf blight. In this study of the aetiology, suscept range and distribution of leaf spot. Alternaria citri and Collerorrichum gloeosporioides were most frequently isolated, often in association with each other, from rough lemon leaves, but only A. cirri caused typical disease symptoms in a screenhouse pathogenicity test. Simultaneous inoculations of leaves with A cirri and C. glocosporinides also resulted in typical leaf spots. Colletoirichum gloeosporioides alone caused leaf specks and is considered non-pathogenic, possibly a secondary invader after A, cirri. Grapefruit, sour orange, sweet orange, tangerine and lime remained disease-free when inoculated with a virulent isolate of A. cirri. A survey of major citrus growing areas in the Ashanti Region confirmed that the disease is limited to rough lemon. It was observed in all areas where the plants could be
found.
In Ghana, seedlings of rough lemon (Citrus limon L.) are grown extensively in nurseries for use as rootstocks in propagating other Citrus species. Cultivation of the plant for its fruits on a commercial basis is, however, not practised. When the plant is grown, usually at citrus research stations, the operation is small-scale, with the aim of utilizing

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This article was published by FAO Plant Production Bulletin, 1991, vol. 39, No. 2/3.